Imagined condition imagined outcome

be If I had been taller I would have joined the police force.

have: If I had had any sense, I would have kept quiet about it.

Past perfect. If we had gone by car, we would have saved time.

Past perfect progressive. If I had been trying harder I would have succeeded.

could have If I could have stopped there wouldn't have been an accident.

We often use 'If I had been you/in your position' expressions to describe a course of action we would have followed in someone else’s position:

If I had been you/in your position, I’d have accepted their offer.

(This means You should have accepted their offer)

We can also use these expressions to refer to somebody else:
If I had been Jane, I’d have walked out on him years ago.

We often use 'If it hadn't been for' expression to explain why something didn’t happen in the past:
If it hadn't been for the rain, we would have had a good harvest.

Inversion with 'had' in Type 3 conditionals

The form Had (he) is a formal variation of If (he) had:

Had the management acted sooner, the strike wouldn’t have happened.

A negative inversion is possible with the full form

Had it not been for the unusually bad weather the rescue party would have been able to save the stranded climber (Not * Hadn’ t *) [6; 288].

In the main clause of Type 3 conditional sentences we may use modal verbs:

'if'-clause: past perfect tense main clause: modal